1. Field of the Invention
The invention relates to a solid electrolytic capacitor.
2. Description of Related Art
FIG. 19 is a sectional view of an example of a conventional solid electrolytic capacitor. As shown in FIG. 19, the conventional solid electrolytic capacitor includes a lead-type capacitor element 81, an outer package member 82 covering the capacitor element 81, an anode terminal 83, and a cathode terminal 84. The capacitor element 81 includes an anode body 811 in the form of a rectangular parallelepiped, an anode lead 812 implanted in the anode body 811, a dielectric layer 813 formed on the outer circumference of the anode body 811, an electrolyte layer 814 formed on the dielectric layer 813, and a cathode layer 815 formed on the electrolyte layer 814. The anode and cathode terminals 83 and 84 are spaced apart from each other in a predetermined direction 89 (horizontal direction in the plane of FIG. 19). Part of a surface of the anode terminal 83 and part of a surface of the cathode terminal 84 are exposed at a lower surface 82a of the outer package member 82. These exposed surfaces of the anode and cathode terminals 83 and 84 form anode and cathode terminal surfaces 830 and 840 of the solid electrolytic capacitor respectively.
In the conventional solid electrolytic capacitor shown in FIG. 19, the capacitor element 81 is placed on the anode and cathode terminals 83 and 84 in such a posture that a pulled-out portion 812a of the anode lead 812 is pointed in the direction 89. The pulled-out portion 812a and the anode terminal 83 are electrically connected to each other through a conductive pillow member 85. Further, the cathode layer 815 and the cathode terminal 84 are electrically connected to each other through a conductive adhesive agent (not shown) provided therebetween. The solid electrolytic capacitor is given a current path 86 extending from the anode terminal surface 830 through the anode lead 812 to reach the cathode terminal surface 840.
In the conventional solid electrolytic capacitor shown in FIG. 19, the anode lead 812 is pulled out substantially through the center of a surface 811b as part of the outer circumference of the anode body 811 through which the anode lead 812 is implanted. So, the aforementioned posture of the capacitor element 81 places the pulled-out portion 812a at a position higher than a lower surface 811a of the anode body 811. To be specific, the pulled-out portion 812a is placed far above the anode terminal surface 830.
So, the conventional solid electrolytic capacitor finds difficulty in shortening the current path 86, placing limitations on reduction of ESL (equivalent series inductance) and/or ESR (equivalent series resistance).
It is preferable that the anode terminal 83 be placed near the pulled-out portion 812a in order to minimize the ESL and/or ESR of a solid electrolytic capacitor. So, if the pulled-out portion 812a is pointed in the direction 89 as in the conventional solid electrolytic capacitor (FIG. 19), the anode terminal 83 should be provided near the surface 811b of the anode body 811. As a result, design of the anode and cathode terminals 83 and 84 including arrangement of the anode and cathode terminals 83 and 84, and connections between the anode and cathode terminals 83 and 84 and the capacitor element 81, should be made with a low degree of freedom.
In addition, in the conventional solid electrolytic capacitor (FIG. 19), a surface of part of the anode lead 812 buried in the anode body 811 is electrically connected to the anode body 811. This makes a contact area between the anode body 811 and the anode lead 812 small so electrical resistance is easily generated between the anode body 811 and the anode lead 812. Also, in the conventional solid electrolytic capacitor (FIG. 19), a side surface of the pulled-out portion 812a is electrically connected to a tip end surface of the pillow member 85. This makes a contact area between the anode lead 812 and the pillow member 85 small so electrical resistance is easily generated between the anode lead 812 and the pillow member 85. So, in the conventional solid electrolytic capacitor, these electrical resistances place an obstacle to reduction of ESR.